Pigments used in ink jet printing applications must be of a small size. The particle size has an influence on the dispersion stability. Further, the Brownian motion of minute particles helps prevent flocculation and settling. The particle size thus should be selected to optimize the stability of the dispersion, consistent with the other requirements of the intended application for the dispersion. In ink jet ink applications, the pigment particles need to be sufficiently small to permit free flow of the ink through the ink jet printing device, especially at the ejecting nozzles which typically have a diameter in the range of 10 to 50 microns. !n addition, it also is desirable to use small particles for maximum color strength and gloss. The useful range of particle size is approximately 0.005 micron to 15 microns. Preferably, the pigment particle size should range from 0.005 to 1 micron. Similarly, the toner utilized in the electrophotographic process is keenly required to have a small particle size pigment for improving its image quality.
As initially produced and isolated, crude quinacridone pigments are generally unsuitable for use in inkjet applications and must be subjected to additional finishing steps that modify the quinacridone pigment particle size, particle shape, and/or crystal structure to provide good pigmentary quality.
Other such uses and applications including but not limited to paints, plastics and toners also require small particle size and good pigment quality.
Thus, there does not exist a process to produce small particle quinacridones having increased transparency and stability in application.